Japan has taken some steps forward since the one-two punch of the earthquake and tsunami that hit the country in March. But the long-term health of the economy, which has continued to decline over the past several years, is facing a new threat that looms larger every day: Japan needs more workers. Birthrates have been plummeting — faster, in fact, than in other developed country — even as the number of older citizens is soaring.As recently as 1990, working-age Japanese outnumbered children and the elderly by 7 to 3. By 2050 the ratio will be 1 to 1. As the population grows old and feeble, the country needs to look to the growing number of educated Japanese women.

Japanese women constitute nearly half (48%) of university graduates. Yet this tranche of talent is woefully underutilized: Only 67% of college-educated women are currently employed, and many of them either languish in low-paid, part-time jobs or are shunted into dead-end “office-lady” roles serving tea for male managers and dusting their desks at the end of the day.

New data from the Center for Work-Life Policy finds that Japanese women with college degrees are muchmore likely than Americans (74% versus 31%) to quit their jobs voluntarily. But while childcare is the primary reason that most Western women take a career break, highly educated Japanese women are more likely to say that they’re pushed off the career track by unsupportive work environments and managers who do not value them. Nearly two-thirds (63%) say that they quit because their career was not satisfying and a startling 49% left because they felt stymied and stalled.

It’s not surprising that when a well-qualified woman is passed over for a plum assignment or is forced to watch a less-qualified male peer promoted before her, the decision to off-ramp and focus on family becomes a no-brainer. But that’s not to say that talented women who have spent years accumulating skills, experience and credentials want to abandon their careers over the long haul. Fully 77% of off-ramped women surveyed want to rejoin the workforce after a relatively short time out.

But on-rampers in Japan tend to run into a wall. Only 43% succeed in finding full-time employment, compared to 73% in the U.S. And, among those lucky enough to land a job, nearly half face cuts in salary and many others are forced to accept reduced management responsibilities and curtailed promotional prospects.

Japanese women who stick with careers find that Japan’s rigid work schedules don’t mix well with the demands at home. Societal expectations of mothers — who not only to tend to the children but also often have to shoulder the brunt of caring for aging relatives — amount to a full-time job. Few get much help from their husbands. On average, working mothers devote more than four hours a day on housework and childcare; working fathers, on the other hand, spent barely 30 minutes. Strict labor laws make it impossible to find affordable domestic help. And unlike counterparts in most developed countries, Japanese working mothers cannot sponsor a foreign nanny for a visa.

In order to retain talented female workers, employers should make flex-time a priority. Two-thirds of the women surveyed say they would not have quit their jobs if flexible work arrangements had been available. But there are also cultural barriers. One respondent, a senior woman who left work at 5:30 in order to pick up her two children before the daycare facility closed at 6:30, said, “The pressure I get is not from my boss; it’s from my male counterparts in other divisions who don’t understand why I need to leave early. I have a BlackBerry and I ask them to e-mail me if they need me, but my colleagues expect me to be there when they call my office.”

For Japanese women wishing to pursue a career, the best bet, at the moment, is to work for a foreign company. The vast majority of women surveyed see U.S.- and European-headquartered firms as having a more female-friendly culture. They particularly appreciate when advancement is based on the quality of work done and colleagues and bosses encourage freedom of expression. “The women here have opinions,” marveled one worker who switched to a multinational corporation. “They talk back. They are direct.”

Japan has been a byword for innovation for much of the last half-century. As the looming demographic crisis threatens to reshape the economy as drastically as any natural disaster, better using its educated women would be an innovation that, according to a 2010 Goldman Sachs study, would add 8.2 million brains to the workforce and boost the economy by 15%. Japanese women are poised to make this happen and looking to employers to lead the charge.